I can read on the page http://cygwin.com/xfree/ "We are now using the SI prefixes for binary files sizes, according to"
<http://physics.nist.gov/cuu/Units/binary.html> But according to this NIST web page, "It is important to recognize that the new prefixes for binary multiples are not part of the International System of Units (SI), the modern metric system. " Yours, O Crumeyrolle.
